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SCI: Lipid Abnormalities (2007)

Citation:

Kjaer M. Dela F, Sorensen FB, Secher NH, Bangsbo J, Mohr T, Galbo H. Fatty acid kinetics and carbohydrate metabolism during electrical exercise in spinal cord-injured humans. Am J Physiol Regul Integr Comp Physiol. 2001;281(5):R1492-1498.

PubMed ID: 11641120
 
Study Design:
Time Study
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
  • To clarify the role of blood-borne mechanisms for free fatty acid mobilization during exercise, and to determine the interrelationships between FFA delivery, FFA uptake, and carbohydrate metabolism in muscle.
Inclusion Criteria:
  • Adult
  • Spinal cord-injured (SCI)
  • Neurologically stable
  • Participated in an ongoing training program for at least 4 months, including regular performance of electrically induced cycling
  • Controls were adult and "healthy able-bodied"
  • Willing to consent to study
Exclusion Criteria:
  • None specified
Description of Study Protocol:

Recruitment

  • Not discussed

Design

  •  Time series study with comparison group

Blinding used

  •  Not applicable

Intervention

  • Catheters were inserted into one femoral artery and one femoral vein.
  • Albumin-bound, isotope labeled palmitate (free fatty acid) was infused continuously intraveneously into the arm.
  • Subjects rested supine for 60 minutes after catheterization, and then rested 15 minutes sitting on the exercise bike. 
  • Subjects exercised for 30 minutes;  SCI subjects used a computer-controlled functional electrical stimulation exercise ergometer (exercise cycle).  The control subjects used the same exercise ergometer and voluntarily cycled for 30 minutes, with their work load adjusted to achieve similar oxygen uptake rate as the SCI subjects.

Statistical Analysis

  • To test whether changes occurred over time, or whether there were overall differences between groups, nonparametric statistical analysis (Friedman's test) was done.
  • Mann-Whitney's test was used to evaluate differences between groups at specific time points.
  • P<0.05 was considered significant.
Data Collection Summary:

Timing of Measurements

  • Muscle tissue needle biopsies were taken above the knee before exercise and immediately after 30 minutes of exercise
  • Blood samples were taken at rest, after 15 and 30 minutes of exercise, and after 15 minutes of recovery.

Dependent Variables

  • Muscle biopsy measurements
  • Laboratory measurements

Independent Variables

  •   Spinal cord injured or control group (not-spinal cord injured)

Control Variables

  •   None discussed
Description of Actual Data Sample:

 

Initial N: 10 spinal cord-injured (SCI): 6 tetraplegic and 4 paraplegic;  6 control subjects

Attrition (final N): n/a

Age: SCI average age: 35 years (27-45); control average age 25 years (20-31)

Ethnicity: Not mentioned

Other relevant demographics: None mentioned

Anthropometrics:  SCI weight 78 (63-87) kg; control weight 76 (68-84) kg

Location: Copenhagen NV, Denmark

 

Summary of Results:

 

Change in select measurements during 30 minutes of exercise

Variables

Spinal Cord-injured subjects

Control subjects

Statistical Significance of Difference

Plasma free fatty acids (FFA) Decreased*# Unchanged

p<0.05

Plasma glycerol

Increased *

Increased*

p<0.05

Specific activity of FFA  

Increased*#

Decreased

p<0.05

Rate of FFA appearance Decreased*# Increased* p<0.05
Insulin and c-peptide Unchanged Decreased* p<0.05
Arterial plasma glucose Decreased*# Unchanged p<0.05

 * change signifiant from rest

# change significant compared to control

Other Findings

  • Leg oxygen uptake was similar in SCI and controls during the exercise.
  • Leg blood flow at rest and during exercise was higher in the control than in SCI subjects.
  • FFA delivery to the legs in the control was 2-3 fold higher in the control than in SCI subjects.
  • At rest, the fractional uptake of FFA was significantly lower in SCI subjects than in control and  decreased significantly in both groups during exercise. 
  • Leg glucose uptake was higher in SCI than control subjects.
  • Muscle glycogen breakdown was higher in SCI than control subjects.

 

Author Conclusion:

FFA mobilization, delivery, and uptake are lower, and glycogen breakdown and glucose uptake are higher in SCI individuals during electrical exercise than in controls performing voluntary exercise.  Carbohydrate oxidation, muscle glycogenolysis, and leg glucose uptake are higher in SCI subjects than in control subjects.  Blood-borne mechanisms are not enough to elicit a normal increase in FFF mobilization.

Funding Source:
Government: Danish National Research Foundation, Danish Medical Research Council, Team Denmark's Research Foundation, Danish Sports Research Council
Not-for-profit
1
Reviewer Comments:

This study was limited by small sample size of both study and control groups.

Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) N/A
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) N/A
 
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? ???
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? N/A
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
3. Were study groups comparable? N/A
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) Yes
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? N/A
  4.1. Were follow-up methods described and the same for all groups? N/A
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? N/A
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? N/A
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) N/A
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? ???
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? No
  6.6. Were extra or unplanned treatments described? No
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? N/A
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? N/A
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? ???
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? N/A
  8.6. Was clinical significance as well as statistical significance reported? No
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? No
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? No
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes